DP Physics (last assessment 2024)

Question 17N.3.HL.TZ0.7

Date	November 2017	Marks available	[Maximum mark: 6]	Reference code	17N.3.HL.TZ0.7
Level	HL	Paper	3	Time zone	TZ0
Command term	Determine	Question number	7	Adapted from	N/A

[Maximum mark: 6]

17N.3.HL.TZ0.7

The ${\Lambda ^0}$ (Lambda) particle decays spontaneously into a proton and a negatively charged pion of rest mass 140 MeV c^–2. After the decay, the particles are moving in the same direction with a proton momentum of 630 MeV c^–1 and a pion momentum of 270 MeV c^–1.

(a)

Determine the rest mass of the ${\Lambda ^0}$ particle.

[4]

Markscheme

$\Lambda$ momentum = 900

E_proton = « $\sqrt {p{c^2} + {{\left( {m{c^2}} \right)}^2}} = \sqrt {{{630}^2} + {{938}^2}} =$ » 1130 «MeV»